Movement across membranes

Question 1

1. how can molecules move in and out of cells.

2. how can water molecules move in and out of cells.

Answer 1

1. diffusion, active transport

2. Osmosis

Question 2

What is diffusion

Answer 2

Diffusion the movement of molecules from a high concentration to a low concentration.

Question 3

what is osmosis

Answer 3

The movement of water molecules from a high concentration to a low through a semipermeable membrane.

Question 4

What is active transport. what does it require to work

Answer 4

The movement of molecule against the concentration gradient from low to high concentration.
It requires energy from respiration as molecules don’t naturally move from a low to high concentration.

Question 5

How does active transport work

Answer 5

works by carrier proteins which are embedded in the cell membrane to move specific molecules against concentration gradient

Question 6

what are the factors affect the rate of movement of substances into and out of cells

Answer 6

surface to volume ratio, distance, temperature and concentration gradient.

Question 7

How does surface area to volume ratio affect the rate of movement of substances into and out of cells

Answer 7

the bigger cell or structure is the less surface area to volume ratio, therefore slowing the rate of which molecules pass through.

Question 8

How does distance affect the rate of movement of substances into and out of cells

Answer 8

smaller the distance molecules have to travel the faster transport will occur.

Question 9

How does temperature affect the rate of movement of substances into and out of cells

Answer 9

Higher the temperature, the faster molecules move as they have more energy. Results in more collisions against the cell membrane and therefore a faster rate of movement across them

Question 10

How does Concentration gradient affect the rate of movement of substances into and out of cells

Answer 10

greater the difference in concentration either side of the membrane, the faster movement across it will occur because the side with the higher concentration, more random collisions against the membrane will occur

Question 11

Investigate Diffusion in a Non-Living System

Answer 11

1. Add crystal (potassium permanganate ) to H2O (solvent)
2. The potassium permanganate particles will diffuse with solvent particles (move from areas of higher concentration to lower concentration), diffusing throughout the solvent
3. The potassium permanganate particles will be less concentrated in one place in the end, so the colour will not be as deep

Question 12

Investigate Diffusion in a Living System

Answer 12

1. Inhalation = O2 air enters the alveoli
2. there is higher concentration of oxygen in the alveoli than in the blood running past the alveoli
3. Oxygen will diffuse out of the alveoli into the blood stream.
4. there is a high concentration CO2(from respiration) in the bloodstream that would diffuse into the alveoli
5. This is how gaseous exchange takes place in mammals

Question 13

investigate Osmosis in a Non-Living System

Answer 13

1. Take a visking bag filled with sucrose solution is placed into a beaker of water
2. Capillary tube is placed in the bag and the level of liquid in the tube is observed
3. Concentration of water particles is higher outside (in the beaker of water) than inside the visking tubing bag
4. Water molecules will move through the partially permeable membrane of the visking tubing down the water concentration gradient.
5. Over time the solution in the bag would rise as the water molecules from the beaker have diffused into the visking bag due to osmosis.

Question 14

investigate Osmosis in a Living System

Answer 14

1. Peel the potato as it could affect osmosis.
2. Use a cork borer to produce 3 cylinders of potato. (makes the diameter of all potatoes the same).
3. Use scalpel to cut potato to same length ( 5cm).
4. Measure the length of each cylinder by using a ruler and a the mass by a balance.
5. Place one of the cylinder in 10cm3 distilled water, and other two in sugar solutions of increasing concentration(0.25 molar and 0.5)
6. Leave the potato cylinder for 20-30 mins allowing osmosis to take place.
7. Take them out and gently dry them using a paper towel to remove surface moisture.
8. Measure the length and mass of each cylinder again.
9. Calculate the percentage change of in length and mass to see the difference.

Question 15

investigation of Osmosis in a Living System results of distilled water

Answer 15

The potato cylinder in the distilled water would have increased mass the most as there is a greater concentration gradient in this tube between the distilled water and the potato cells. The water molecules outside the potato will move down the concentration gradient into the potato by osmosis making them turgid and increasing the mass of the cylinder

Question 16

investigation of Osmosis in a Living System results of concentrated sucrose solution.

Answer 16

potato cylinder in the strongest sucrose concentration will have decreased its mass the most as there is a greater concentration gradient of water in this tube between the potato cells than sucrose solution. Therefore the water molecule inside the potato will move out causing the cells to be flaccid, decreasing the mass.